One of the central problems of personal identity is to determine what we are essentially . In response to this problem, Lynne Rudder Baker espouses a psychological criterion, that is, she claims that persons are essentially psychological. Baker’s theory purports to bypass the problems of other psychological theories such as Dissociative Identity Disorder and the problem of individuating persons synchronically. I argue that the theory’s treatment of Dissociative Identity Disorder leads to untenable results, is invalid, and consequently fails to individuate persons